An Error Vector Magnitude (EVM) test is a transmitter modulation quality metric for electronics such as communications (e.g., cellular, wireless local area network (WLAN), paging, and the like) electronics, such as embodied in integrated circuits (ICs), multi-chip modules, and chipsets. In general, the transmitted EVM is measured via a comparison of an input demodulated constellation point to an ideal constellation point, given a proscribed filtering, etc., and after error-compensation. The EVM test may be used to measure deviations of the output waveform voltage (e.g., of the IC, multi-chip module, chipset, etc.) from an ideal waveform at the exact data-slicer sample time and after equalization and signal conditioning has been performed. Using the measured deviations, modifications to the IC, multi-chip module, or chipset may be made to correct for such deviations. Additionally, such deviations may be used as a quality metric in regulator acceptance testing or, when compared to acceptance limits, for production pass/fail testing.
One concern is whether the EVM test results are representative of the actual deviations from ideal. The IC, multi-chip module, or chipset performs most of the demodulation and data slicing for demodulating a received signal using digital signal processing (DSP) techniques often utilizing fixed-point software or hardware filters and calculation blocks. Disparities in EVM test results may exist between EVM tests performed using test equipment external to the IC and the actual transmit modulation/receive demodulation quality of the transceiver IC or chipset. For example, external test systems use proprietary down-conversion, demodulation, and baseband signal extraction algorithms that are typically different from the fixed-point hardware down-conversion, demodulation, and baseband extraction algorithms performed by the communication IC. In some instances, the derived voltage using the test equipment may differ from the derived voltage produced by the communication IC. The actual deviation within the IC may be different from the deviation detected by the test equipment, and thus the EVM result may be non-indicative of the transceiver IC or chipset quality. Additionally, because the baseband signal extraction algorithms typically vary from one test equipment vendor to another (e.g., producing different EVM results), correlating results with customers using different EVM test equipment is a difficult process.
EVM tests may be used to evaluate the magnitude of deviations of the IC waveform voltage from the ideal waveform during production as an acceptance gate. For example, devices that pass the EVM test are deemed shippable product while those devices that fall short of the EVM test are recycled. From a production test time perspective, conventional EVM tests take a considerable amount of time which increases IC production costs. Much of this test time may be attributed to the fact that the conventional EVM test equipment first digitizes the transmitted signal and then post-processes the digitized signal to calculate the EVM.
Test system vendors typically develop EVM solutions on an as-needed basis. The proprietary algorithms of each Automatic Test Equipment (ATE) vendor are typically individually developed as the need arises, and these algorithms often take several months to develop and several more months to correlate. This development and correlation time often adversely impacts production delivery schedules. For example, delivery of the EVM test results can take about four (4) to six (6) months and then take a few more months for correlation and prove-in. Conducting EVM tests in a production environment is generally a time consuming and costly process. Volume EVM testing is typically not available early enough in a device design cycle to permit design fixes based upon the EVM results. Additionally, the test system should be fully configured for modulated radio frequency (RF) source and measurement capabilities which is expensive to implement.
Accordingly, systems and methods for testing electronics are desired that provide a representative quality metric. More particularly, in some examples, systems and methods for EVM testing of ICs or chipsets are desired that provide a representative quality metric in real time. In addition, systems and methods for testing communication electronics are desired that provide a representative quality metric while reducing correlation difficulties. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.